Phosphonic acid reaction products and use in coating compositions

ABSTRACT

The invention provides an aqueous coating composition comprising nonionically and/or anionically stabilized film-forming polymers and metallic pigments and a compound which is the reaction product of a phosphonic acid derivative, a hydroxy-functional addition polymers and, optionally a compound having a hydroxy group, in which the phosphonic acid derivative is selected from one or both of                    
     wherein R and R′ are selected from the group consisting of an aliphatic and an aromatic substituent having 1 to 25 carbon atoms optionally including heteroatoms of at least one of oxygen, phosphorus and silicon.

This application claims the benefit of provisional application ser. No.60/054,179 filed Jul. 30, 1997.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 4,675,358 discloses coating compositions employingphosphoric acid derivatives. Such compositions are not veryhydrolytically stable. WO 96/08518 describes N-acyl aminomethylenephosphonates and derivatives and their use in waterborne coatings. Suchcompositions have limited compatibility with other binders and limiteddurability because of N-containing linkages. EP 391,230 disclosescompounds which are the reaction product of an alpha-aminomethylenephosphonic acid with an epoxy group of a compound containing at leastone epoxy group. Such reaction products have limited end use inwater-borne compositions that are anionically stabilized since the aminogroup destabilizes the coating composition. U.S. Pat. No. 5,151,125discloses aqueous metallic coating compositions comprising acryliccopolymers to reduce the gassing of aluminum flakes. Such compositionshave limited hydrolytic stability and limited effectiveness.

SUMMARY OF THE INVENTION

We have found that hydrophobic-substituted phosphonic acid derivativeswhich are reaction products with hydroxy-functional copolymers areparticularly effective for inhibiting the corrosion of metallic pigmentsin water-borne compositions. The invention concerns an aqueous coatingcomposition comprising a stabilized film-forming polymer, a metallicpigment and a compound which is the reaction production of a, b andoptionally c, wherein:

(a) is 5 to 95 weight percent of a phosphonic acid derivative consistingof one or both of

wherein R and R′ are selected from the group consisting of an aliphatic,cycloaliphatic and aromatic substituent having 1 to 25 carbon atoms andoptionally up to 10 heteroatoms of at least one of oxygen, phosphorusand silicon;

(b) is 5 to 95 weight percent of a hydroxy-functional addition polymerwith a weight average molecular weight of 1000 to 30,000; and

(c) is 0 to 90 weight percent of a compound having onehydroxy-functional group.

Representative examples of phosphonic acid group-containing compoundsare vinyl phosphonic acid, propyl and octyl phosphonic acid, andhydroxyethane diphosphonic acid.

Representative examples of hydroxy-functional polymers are additioncopolymers of methacrylates, vinylaromatics, acrylates,acrylamides/methacrylamides and their derivatives, acrylonitrile,methacrylonitrile, allylalcohol, maleates, itaconates and vinylmonomers. The copolymers are hydroxy and/or acid functional. Typicalcomonomers useful to obtain the hydroxy-functionality are 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxy propyl acrylate,2-hydroxy propyl methacrylate, allyl alcohol, 1,4-butenediol,4-hydroxybutyl acrylate, bis-hydroxy ethyl maleate and the like.Preferred hydroxy-functional copolymers are copolymers of styrene andallyl alcohol. A preferred phosphonic acid derivative is propyl andoctyl phosphonic acid.

The hydroxy functional copolymers are typically prepared in afree-radical initiated process using peroxy or azo initiators. Thereaction between the hydroxy functional copolymer and the vinyl and/oralkyl phosphonic acid can be run in a fusion or solvent process wherewater is distilled.

The reaction products of the phosphonic acid derivatives and thehydroxy-functional copolymers are used to treat metallic pigments beforethe final blend is inverted in water. The final metallic pigmentdispersions are stable from gassing.

DETAILED DESCRIPTION

Preferred coating compositions are the following:

where the reaction product as corrosion inhibitor is used in the form ofa salt;

where the phosphonic acid derivative is propyl, octyl or vinylphosphonicacid;

where the hydroxy-functional product is based on a styrene-allylcopolymer;

where the corrosion inhibitor based on phosphonic acid has an acid valueof 25 to 400 mgKOH/g;

where the composition is anionically or non-ionically stabilized, andwhere the film-forming polymers are anionically stabilized vinyl,acrylic and/or urethane emulsions.

Preferred phosphonic acid group-containing reaction products are thoseformed from one or more of vinyl phosphonic acid, propyl and octylphosphonic acid, and hydroxyethane diphosphonic acid with one or morehydroxy-functional copolymers of styrene and allyl alcohol. Preferably,R and R′ have up to 12 carbon atoms and effect goodhydrophilic-lipophilic balance (HLB).

EXAMPLES Example 1

In a reaction vessel fitted with stirrer, thermometer, reflux condenserand Dean and Stark separator, a mixture of 300 parts xylene, 300 partsstyrene/allyl alcohol copolymer commercially available from ARCOChemicals under the trade name ARCO SAA 100 resin having a numberaverage molecular weight of 1600 and a hydroxy number of 210 was heatedat 85-90° C. till dissolved. There was then added 129.33 parts of octylphosphonic acid (80% solution in water/ethanol=1/1). The temperature wasraised to reflux (±148° C.) while water was removed. After 2 hours, 16parts of water had been removed and the contents of the reactor werevacuum stripped. The reaction product was diluted with 270 parts of2-butoxyethanol.

Test Results:

Solids 58.8% Viscosity (Gardner Holdt) W Acid value 148 mgKOH/g NumberAverage MW 1700 Weight Average MW 4400

Example 2

Procedure of Example 1 was repeated using 300 parts xylene, 300 partsaforedescribed ARCO SAA 100 resin, i.e., styrene/allylalcohol copolymer,215.55 parts octyl phosphonic acid. In total, 28 parts of water werestripped in about 2 hours. After vacuum stripping, the reaction productwas diluted in 310 parts of 2-butoxyethanol.

Test Results:

Solids 59.7% Viscosity (Gardner Holdt) V - 1/4 Acid value 188 mgKOH/gNumber Average MW 1300 Weight Average MW 3800

Example 3

Procedure of Example 1 was repeated in which 240 parts styrene/allylalcohol copolymer were reacted with 73.8 parts of p-tert amylphenol and137.33 parts of Cublen® K60 in 350 parts of xylene. Cublen® K60 is a 60%solution in water of hydroxy ethane diphosphonic acid from Zschimmer andSchwarz Company.

Test Results:

Solids 58.4% Viscosity Y Acid value 184 mgKOH/g Number Average MW 1560Weight Average MW 4260

Example 4

Procedure of Example 1 was repeated in which 100 parts xylene, 300 partsof styrene/allyl alcohol copolymer and 85 parts of vinylphosphonic acidwere used.

Test Results:

Solids 59.8% Viscosity Z2 Acid value 178 mgKOH/g Number Average MW 1100Weight Average MW 2400

Example 5 Styrene/Allyic Alcohol Copolymer Modified with PropylPhosphonic Acid

Into a 500 ml 3-neck round bottom flask fitted with a reflux condenser,water separate and air driven stirrer place the following and heat to80-90° C. until dissolved:

Xylene 50.0 grams ARCO SAA100 resin 100.0 grams  (commerically avaliablefrom ARCO Chemicals) Add the following and raise temperature to reflux(˜148° C.): propyl phosphonic acid 36.2 grams

Continue to heat for 2 to 3 hours when approximate 5.6 grams of waterwill have been removed by azeotropic distillation. Cool to 100° C. andbegin vacuum strip to remove about 50 grams of solvent. At the end ofthe distillation, add the following to the reactor and allow to cool.

Butylcelosolve  90.0 grams Fill out into a plastic container. ProductAcid Number 145 Weight Solids  59%

Example 6

Paint Example: Parts: Dispersions Inhibitor Example 2 7.83 Butyl Glycol58.42 Alu Flake (1) 30.75 Dimethylethanolamine 1.50 Thickener (2) 1.50Aluminum Based Paint Dispersion of Inhibitor of Example 2 24.03 Latex(3) 27.53 D.I. water 47.55 Defoamer (4) 0.01 Thickener Combination (5)0.88 Gassing Results (6) After 1 week OK After 2 weeks OK After 3 weeksOK After 4 weeks OK (1) Stapa Metallic R-607 @65% solids commerciallyavailable from Eckart (2) NOPCO DSX 1550 commercially available fromHenkel (3) Anionically Stabilized latex available from DuPont Company(4) Balab 3056A commercially available from Witco (5) ASE-60 Thickenersupplied by Rohm and Haas Company and Polyphobe PP-107 :78/22. suppliedby Union Carbide (6) ALU Paint is mixed with iron oxide dispersion andkept in closed container at 49° C.

Example 7

Paint Formula: Parts: Mineral spirits  4.9 (boiling range 140-160° C.)Ethylene glycol-mono-n-hexylether  4.9 Ethylene glycol-mono-n-butylether10.9 Aluminum Flake 17.8 (Silverline ® SSP-353) (course aluminum flake70% solids) Inhibitor of Example 2  4.3 Acrylic latex 30% in water 61.5(Adjust till pH is 9) with  0.90 aminomethylpropanol The gassing wasfollowed by measuring  5.3 ml the ml of hydrogen (H₂) generated in 16hours at 60° C.

What is claimed is:
 1. An aqueous coating composition comprising astabilized film-forming polymer, metallic pigments and a corrosioninhibitor which is a hydrophobic-substituted reaction product of (a) and(b), wherein: (a) is 5 to 95 weight percent of a phosphonic acidderivative consisting of one or

wherein R and R¹ are free from nitrogen atom and are selected from thegroup consisting of an aliphatic, cycloaliphatic and aromaticsubstituent having 1 to 25 carbon atoms and optionally, Up to 10heteroatoms of at least one of oxygen, phosphorus and silicon; and (b)is 5 to 95 weight percent of a hydroxy-functional addition polymercomprising a styrene-allyl alcohol polymer having a weight averagemolecular weight of oxygen 1,000 to 30,000; wherein said metallicpigments in said aqueous coating composition are stabilized from gassingfor three weeks.
 2. A composition of claim 1 where the reaction productis in the form of a salt.
 3. A composition of claim 1 where thephosphonic acid derivative is selected from the group consisting ofpropyl phosphonic acid, octyl phosphonic acid, and vinyl phosphonicacid.
 4. A composition of claim 1 where the corrosion inhibitor has anacid value of 25 to 400 KOH/g.
 5. A composition of claim 1 where thefilm forming polymers are selected from the group consisting ofanionically stabilized vinyl emulsions, anionically stabilized acrylicemulsions and anionically stabilized urethane emulsions.
 6. The aqueouscoating composition of claim 1 wherein said corrosion inhibitor is ahydrophobic-substituted reaction product of said (a), said (b) and 0 to90 weight percent of a compound having one hydroxy-functional group. 7.The aqueous coating composition of claim 6 wherein said compound isp-tert amylphenol.
 8. An aqueous coating composition comprising astabilized film-forming polymer, metallic pigments and a corrosioninhibitor which is a hydrophobic-substituted reaction product of (a) and(b), wherein: (a) is 5 to 95 weight percent of hydroxyethanediphosphonic acid and (b) is 5 to 95 weight percent ofhydroxy-functional addition polymer comprising a styrene-allyl alcoholpolymer having a weight average molecular weight of 1,000 to 30,000;wherein said metallic pigments in said aqueous coating composition arestabilized from gassing for three weeks.
 9. The aqueous coatingcomposition of claim 8 wherein said corrosion inhibitor is ahydrophobic-substituted reaction product of said (a), said (b) and 0 to90 weight percent of a compound having one hydroxy-functional group. 10.The aqueous coating composition of claim 9 wherein said compound isp-tert amylphenol.